drm: Make the .mode_fixup() operations mode argument a const pointer

The passed mode must not be modified by the operation, make it const.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/i2c/ch7006_drv.c b/drivers/gpu/drm/i2c/ch7006_drv.c
index d3f2e87..36d9522 100644
--- a/drivers/gpu/drm/i2c/ch7006_drv.c
+++ b/drivers/gpu/drm/i2c/ch7006_drv.c
@@ -88,7 +88,7 @@
 }
 
 static bool ch7006_encoder_mode_fixup(struct drm_encoder *encoder,
-				      struct drm_display_mode *mode,
+				      const struct drm_display_mode *mode,
 				      struct drm_display_mode *adjusted_mode)
 {
 	struct ch7006_priv *priv = to_ch7006_priv(encoder);